Year Percent 1975 0.54019 1976 0.54509 1977 0.48516 1978 0.62907 1979 0.54722 1980 0.4906 1981 0.54831 1982 0.64037 1983 0.7306 1984 0.84247 1985 0.92583 1986 1.18452 1987 1.14323 1988 1.19774 1989 1.19303 1990 1.05843 1991 1.29777 1992 1.37862 1993 1.4809 1994 1.83043 1995 1.78707 1996 1.79243 1997 2.00402 1998 2.18089 1999 2.33325 2000 2.26265 2001 2.2382 2002 2.20332 2003 1.92768 2004 1.66536 2005 1.39541 2006 1.09424 2007 0.97667 2008 0.82731 2009 1.03689 2010 0.73503 2011 0.65142 2012 0.62794 2013 0.63317 2014 0.62872 2015 0.72367 2016 0.75086 2017 0.76176 2018 0.71146 2019 0.74671 2020 0.96389 2021 0.94342 2022 0.82374